Such gas bag module comprises a housing, a gas bag arranged therein, a gas generator for filling the gas bag with compressed gas and a cover which closes the housing with respect to the interior of the vehicle and is opened after activation of the gas generator, in order to enable the gas bag to emerge from the housing.
In conventional gas bag modules, after activation of the gas generator, the cover is opened by the force which the gas bag, acted upon by the compressed gas and unfolding, exerts onto the cover. As the cover of the gas bag module in the normal operation of the vehicle is to be not visible, as far as possible, usually a continuous material layer is constructed on that face of the cover which is visible from the interior of the vehicle, which material layer is provided with predetermined breaking points. To open the cover, firstly the continuous material layer has to be overcome. The result of this is that after activation of the gas generator, only a comparatively high pressure has to build up inside the gas bag, before the continuous material layer yields and the cover can open so that the gas bag can unfold inside the vehicle. This pressure, which is reached before the cover is opened, is very much higher than the pressure which occurs during the following unfolding process of the gas bag, in its interior. This excessively high pressure before the start of the opening process of the cover has proved to be disadvantageous from many points of view. From the high pressure, high contact forces result between the gas bag and the cover, for which reason special precautions have to be taken that the gas bag, tearing open the cover, is not damaged by the cover. In addition, the initially excessively high pressure is disadvantageous for the manner in which the gas bag unfolds and positions itself inside the vehicle.